Assuming that the reservoirs are dense, their new operators are
assigned energies that are the same as those before diagonalization.
The D and A (new) energies are assumed to be placed within a band of
continuous states, excluding the existence of bound states. The old
operators are related to the new ones by [1]}
\(c_d&=&\sum _{l}\lambda _l a_l, \,\,\,\,\,\,\ c_l=\sum _{l^{\prime }}\eta _{l,l^{\prime }}a_{l^{\prime }} \nonumber \\c_a&=&\sum _{r}\lambda _r a_r, \,\,\,\,\,\,\ c_r=\sum _{r^{\prime }}\eta _{r,r^{\prime }}a_{r^{\prime }},\) 
